Targeting vectors are protected against the neutralizing antibody K71.

<p>Equal amounts of physical particles of the indicated vector types were incubated in presence of increasing amounts of antibody K71 (K71-Ab; putative epitope near the mutation sites in H_mut-scFv constructs) and L77 (L77-Ab; putative epitope distant to the mutation sites in H_mut-scFv constructs), respectively, in a final volume of 100 µl. After incubation at room temperature for 1 h, (<b>a</b>) 3×10⁴ (CD20-LV) or 4.5×10⁵ (MV_NSe-LV) CD20-positive Raji cells were added, or the vectors were added to (<b>b</b>) 9.3×10⁴ (CD105-LV) or 3.4×10⁴ (MV_NSe-LV) CD105-positive HT1080 cells or (<b>c</b>) 3.4×10⁴ (CD133-LV) or 2.7×10⁴ (MV_NSe-LV) CD133-positive HuH7 cells, to apply an MOI of 0.25 for each vector type. Forty-eight hours later, the fraction of EGFP-positive cells was quantified by FACS analysis. Mean values (n = 3) and s.d. of the relative transduction efficiency compared to transduction in absence of antibody is shown for each cell line. (<b>d</b>) The indicated H proteins were expressed on the surface of HEK-293T cells. The control antibody K83 and the antibodies K71 and L77 were incubated with the cells, respectively, and a FITC-labeled secondary antibody was used to detect antibody binding to the different H proteins by FACS analysis. The percentage of FITC-positive cells subtracted by the staining of secondary antibody alone is shown. Arrows indicate 0% cell staining.